While Spacey lumbers, Goldblum strolls. When Goldblum drawls, Spacey spits. In one of the most exciting locking of male antlers on stage for years, Kevin Spacey and Jeff Goldblum have created a surefire hit for the Old Vic. Their gladiatorial exchanges are so hot, and so linguistically gymnastic, that they almost disguise the fact that this is a lazy play, one which has a big, woman-shaped gap at its centre.

David Mamet's Speed-the-Plow was first performed 20 years ago in New York, with Madonna in the part of the girl or, more accurately, hinge, trigger, fought-over plot device. She's the secretary (complete with notepad, stilettoes and willingness to fetch coffee) who nearly fractures the lives and careers of two movie producers. Goldblum and Spacey - studio boss and struggling producer - are high on the conviction that with a bankable star and a totally crap script about rape in prison, they're about to hit the big time: 'We're going to have to hire someone just to tell us what we want to buy.'

There's a bet between the guys (buddies, they'd call each other) about whether the secretary can be bedded. But the secretary - a hard-to-make- out and sometimes hard-to-hear Laura Michelle Kelly - proposes that instead of the prison movie they should make a morally uplifting (or at least morally tendentious) movie about radiation, fear and God. She nearly pulls it off: she shakes Goldblum's sense of himself, but in an inquisitorial, violent and here thrilling exchange, Spacey succeeds in dissing her, by suggesting that the hustled can also be hustlers.

Practically everything is rickety in this scenario. The girl's redemption-through-disaster movie is such gobbledegook that it's painful to have to listen to it; she's either a naive fool or a calculating minx who's presenting her power hunger as principle. Mamet leaves room - in a role that is not so much richly ambiguous as underwritten - for both interpretations but, either way, it's impossible to believe that a hard-boiled studio boss would be swayed for a minute by her sloppy advocacy. The central point demonstrated in the play is beyond platitude: who's going to get an electric thrill at the news that Hollywood is commercial, cut-throat, anti-art and anti-bleeding-hearts?

What's not rickety is the testosterone-fuelled dialogue. It's both convincing and excluding: listening to it is like being trapped on some terrible, all-male squash court (poor old Laura Michelle Kelly just gets flat slabs of prose). It's hard to believe that Mamet has ever been more fully incarnated than here, where Spacey and Goldblum bark and snarl at each other's sentences as if they were tugging at opposite ends of the same piece of meat.

These are great performances. Those used to seeing Spacey, with his dancer-like grace, dominate the stage will witness something different here. He is a version of Willy Loman, a guttering thing. He manages to suggest (he truly is a great actor) that he's a quite other physical being than the Spacey we've seen before: stumpier, pinker, heavier, round-shouldered, always in danger of slumping and yet with a sort of desperate resilience. He flings himself to the ground to do a quick series of press-ups, co-ordinated with drawing on a cigarette. A mixture of hope and anxiety propels him round the stage in an hysterically weary bounce, like a boxer at the end of a bout, and gives his voice, too, notes of hysteria - he roars and bellows, but just as often yelps. It is a defining, important performance.

Meanwhile, Goldblum moves as if all his limbs are on casters: when his hips swivel, it seems a matter of quizzical surprise to his head; his arms are so long that his hands might be operated by someone else on the other side of the stage. He uses his height to dominate, apparently without effort; confronting the not-at-all short Spacey, he moves close to him and peers down with heron-like elegance, making him look stocky. He comes on to the girl with the same lean insouciance, approaching her and gently looming (he's like a crass version of Samuel Beckett) and with a fine comic touch rearranging the massive pillows for love-making at the same moment as he chats about scripts.

Matthew Warchus's production tries to boost the woman's credibility. Rob Howell's design is intent on making her look candid in her big scenes; she's seen in an angel-like pose - in white, kneeling on a bed looking prayerful - within a set that (all glass tiles and desks) is suddenly made open to the heavens. This doesn't redeem the play from misogyny, which is not an incidental blot, but an irredeemable flaw. But misogyny in action, in speech, can be riveting. As it is here.